STP question with Nexus 5000s

[lonmc1977]

So I'm a little new to the Nexus world and I'm T-shooting some things.  I have two 5548 Nexus's (On one VPC) with 3 - 3750 switches plugged into each Nexus, so all 3 have 2 paths to each Nexus.  

As I understand it, they should all be forwarding packets to each Nexus and not blocking on any ports since both Nexus are on one VPC.  Is that true, and if so why are my 3750's each blocking on one port and forwarding another like any typical STP? 

Thanks for any input.

[Reza Sharifi]

If VPC is configured correctly between the 5500 and also between the 3750s and the 5500 switches, there should not be any port blocking.

What is the output of "sh vpc"  and "sh run vpc" on both 5500s?

Also, can you post reverent configs from both 5500 and also 3750s?

HTH

[lonmc1977]

I attached what I have, I included one 3750 since theyre all the same setup

[Reza Sharifi · Accepted solution]

On the 3750, the ports that connect to both Nexus switches (1/1/1 and 1/1/2) need to be in a Portchannel. You also need to do the same on the Nexus side. Use LACP on both sides.

HTH

[lonmc1977]

Figured it was something like that, thanks